For six years, Seattle-based director Lynn Shelton has been creating intimate movies that look at the lives of friends and lovers. These movies were made with a small crew (mostly made up of her friends) and encouraged a highly collaborative and improvisational approach from the actors. The success of Shelton’ 2009 film Humpday, a comedy of sexual awakening starring Mark Duplass and Joshua Leonard, proved her style could cross over to general audiences, and after directing episodes of Mad Men and New Girl, Shelton’s confidence in her abilities rose along with her status in the industry. For her latest film, Your Sister’s Sister, she’s brought a name actress into the fold: Emily Blunt plays Iris, who hopes to help her friend Jack (Duplass) get over his brother’s death by letting him stay at her family’s empty holiday cabin. But when Iris arrives at the cabin, she unexpectedly finds her sister Hannah (Rosemarie DeWitt) there with Jack. Shelton spoke with The A.V. Club about her interest in bizarre storylines, how a last-minute casting change put the film in jeopardy, and what she thinks of the French remake of Humpday.

The A.V. Club: You seem to have an interest in stories that don’t seem believable, yet you strive to make your films authentic. Are you attracted to the idea of meshing the two?

Lynn Shelton: Truth be told, I hear stories every day that would make you say, “If you put that in a movie, you wouldn’t believe it.” Real life really is kinda incredible; the stories from people’s actual lives defy credibility. People’s lives are messy, humans are messy, and they’re flawed. Everyone tries their hardest, but things tend to not go easy. So maybe that’s one of the reasons why I’m attracted to those stories. What I like is, there’s something in those stories that rings true to me. So my attraction is the challenge of taking something that looks a bit unbelievable on paper, and then making a movie that tells the story in a totally credible way, that makes you every step of the way go, “Yeah, I believe this.”

AVC: Mark Duplass came up with the kernel of an idea for Your Sister’s Sister. What was it, and how did you expand it?

LS: It was: A guy and a girl are best friends; the guy is in a bad place because his brother had recently passed away, and his best friend sends him up to her family’s remote getaway to be by himself and get his head together. He gets up there, and unexpectedly there’s somebody there, and it’s her hot mom. [Laughs.] And then the daughter, the best friend, shows up, and it turns into this love triangle. So pretty much the first thing I did was make the mom into a sister.

AVC: Were you against the cougar-mom angle?

LS: I was open to it for about two seconds; it was just an instinctive thing. One of the things, frankly, that I recognized or was interested in—and how the movie ended up being—was with making the mom a sister, you have these two sets of siblings. So the dead brother is a presence in the film. Even though he’s barely talked about, he weighs so heavily on Jack’s soul, and he informs so intimately how he responds and interacts with the two sisters. I just recognized that the sisterly relationship was going to be really great territory. I think that’s what made me drop the mother thing.

AVC: Because your process is so heavily based on preparation with the actors in pre-production, were you able to get enough time with Emily Blunt leading up to shooting?

LS: The thing that gave me confidence about being able to invite someone who is that busy or not that accessible into the process is, though I was in contact with the actors, it isn’t like a Mike Leigh movie where he’s workshopping every day with them for six months; it’s not a lot of investment in actual time. I had a treatment that I shared with everybody, then I called them up and had conversations with them. But I’m talking like, a one-to-one-and-a-half-hour conversation every few weeks over the course of several months. And we had a weekend workshop, but really, it was all of us just hanging out and getting to know each other’s rhythms and telling stories. This is where the process becomes very personal for everybody, and they can really bring themselves into it and be more invested in the project and the characters. That’s what I hope makes the film resonate; it will feel authentic, that these are real people.

AVC: Rachel Weisz was originally cast to play Hannah. Did you develop the character with her before she had to drop out?

LS: Yeah, she was in that process up until three days before the shoot. [Laughs.]

AVC: Did you feel you could still make the film once she left?

LS: At first blush, I really thought this project couldn’t be done without Rachel. And then an hour later, my first [assistant director] Megan Griffiths was like, “What if we can find somebody?” I didn’t see how this was possible. But then I thought, “I do have a 70-page outline.” For Humpday, we had a 10-page outline because the cast had veteran improvisers; this time, the actresses and I really wanted to have words to fall back on, so I wrote dialogue. And I also had this actual character bible. The good thing about it was, Rachel and I had done such a thorough job, and we had developed such an explicit history [of the character]. And luckily, they were really supposed to be half-sisters, even though Emily and Rachel are both British. It was actually better in a way that Rose is American, because I didn’t even have to change anything. So we were going over names of people, and when Rose’s name came up, she went straight to the top of the list.

AVC: Why was that?

LS: It’s a complicated process if somebody hasn’t seen Humpday or movies like that; they have to be versed in what it is and be attracted to it. And Mark was great; he said, “If Rose is available, she will do it.” Because she accosted him once in an airport and said, “I usually don’t do this, but I just saw Humpday, and I loved it.” So then it was just a matter of working it out with The United States Of Tara, because she was in the middle of doing that show. We had to fly her back and forth twice. So we lost two days; we shot this in 12 days instead of 14. But she was unbelievable. I had a conversation with her for a couple of hours, and she flew up the next day, met Mark on the plane, and then we were shooting.

AVC: Were you concerned that she and Emily would not hit it off?

LS: That was the most amazing thing of all this, how she and Emily had instant chemistry. They are the kinds of human beings—and actors—that are extremely accessible and open, and [they] were both so willing that I feel like that really saved the whole project. If either of them were closed off, it would have never worked. It also helped that the whole cast and crew were sleeping on this little compound of three houses. Emily and Rose had their own house, so they could come hang out with us in the lodge where everyone was. And they ate with us, but they could also get away and just spend quality alone time together, and that ended up being essential. This is where Rose was able to bring her input into the character and into the story.

It was a great lesson for me, because I learned you can not only recast one of the parts, but shoot out of order. Humpday was shot in order, and I thought that was an essential part of this process. It turned out it was helpful to shoot a scene that’s later in the story first, because you had something to aim for.

AVC: What did you learn from Humpday that changed how you made Your Sister’s Sister?

LS: It’s a project-to-project-based thing. Humpday was shot entirely in single shots. We had a camera over each person’s shoulder, and it’s completely improvised. Shooting this way, you have the ability to match the different takes. This time, I really wanted to have more of a variety of shots. It worked for Humpday, because it’s intimate, and there’s tension. With this film, I wanted to back up and see wide shots and get a sense of place, a sense of their physical isolation. So I knew I was going to have a very different approach to the shooting. When you have everything mapped out in a drum-tight script, it’s a lot easier to shoot a scene in many different ways and put it all together later. This is a little more difficult because the shots might be different every time; with improv, it’s a little bit loose. In a traditional film, usually you start with the master, and then you go in closer and closer. We did the opposite because, a lot of the time, the best stuff came in the first take. There may be a surprise that you’ll never be able to recreate, so you want to have the tighter shots first. That was my big goal, to try to have less handheld footage and less close-ups.

AVC: Has directing TV changed the way you make your films?

LS: I’ve been so out of the system. [Laughs.] I feel like I’ve been up in the hinterlands, and everyone went to film school, so I’ve just been creating my own style. But with Mad Men, I remember lobbying so hard to be a guest director. I knew I was in the running, but when they actually gave me the job, I had this moment where I thought, “Oh God, I hope I can do this.” I wondered if the skill set would overlap. I found it incredibly helpful to work with professionals who had a lot of experience and worked with a lot of directors. For instance, one thing that directly affected Your Sister’s Sister was losing those two days; I was terrified, and it seemed impossible to get the amount of footage we needed. But I was told by so many people on Med Men and New Girl that I was the fastest director they’d ever seen. That gave me the confidence that we could make the film in 12 days.

It was incredible on Mad Men to have a script. I just didn’t know how stressful it was to write the words on set. I really got drawn to that idea; I thought maybe I should be more open to [writing a script]. So having a scaffolding to work off of with Your Sister’s Sister was very helpful, and there were times when we’d talk about how to do a scene, and Emily and Rose would say, “What you wrote is great; let’s just go with this.” I became much more comfortable working with words on a page because of Mad Men.

AVC: Your next movie, Touchy Feely, is an ambitious project featuring multiple storylines. Is this the most structured film you’ve done so far?

LS: Yeah. I’d made three films in a row with one location and three characters. I like that and want to go back to it, but I really wanted to see if I could take the model—in terms of intimate crew and work locally— and see if I could do it with an ensemble cast and explore really specific scenes. It just has a very different feeling, this film. And many more scenes and locations. It’s also shot in a much more traditional way.

AVC: So what do you think about the French remake of Humpday?

LS: Oh, [director] Yvan [Attal] was so lovely. He got in touch with me about a year ago. I guess a few of his films have been optioned to be remade in America, and he had a real sense of anxiety because what if he hates the remake? So he got in touch with me and said, [adopts a French accent] “Oh Lynn, you must be very nervous with what I will do with your film.” And I said, “I’m honestly astounded and amazed and delighted.” I watched all his films, and I trusted him. But he wanted me to come on set and be in the movie. I had just finished shooting New Girl and had a week off, so I zipped over there for a couple of days. But it’s a big, like 5 million euro production with big-name French actors, including Charlotte Gainsbourg. I think it’s opening in France in September.

AVC: Are you in the film?

LS: No. By the time I got there, it was the hotel-room scene. The weirdest thing was, he shot the whole thing on location, but they couldn’t find a hotel chain to let them shoot the scene, so they had to do it on a soundstage. So I’m on the soundstage watching this, and I had never gotten over my jetlag. The whole time I sat at the monitor, listening to French that I only 5 percent understood and realizing most of it was translated from my film. So I’m hearing these words and I’m like, “They are doing it exactly word for word!” [Laughs.] But he added scenes, which were so spot-on they should have been in my movie. It was great. He came up to me and said, “I don’t think I betrayed you.” I said, “No, you didn’t at all.”